Injection molding techniques utilizing fluid channels

ABSTRACT

The present invention provides processes and an apparatus for injection-molding an article with a fluid channel formed therein. The process includes providing at least first and second resin streams within a mold cavity, causing the flow fronts ( 16 ) of the resin streams to meet at a longitudinal point in the mold cavity to form a first layer of solidified resin on a peripheral surface of the mold, the first layer having a knit line ( 20 ) at the longitudinal point where the resin streams meet; and introducing a fluid into the molten resin in the mold to form a fluid channel ( 50 ) and a second layer ( 32 ) of solidified resin, the second layer between the fluid channel and the first layer of solidified resin, wherein the second layer is devoid of a knit line at the longitudinal point in the mold cavity where the first and second flow fronts meet.

RELATED APPLICATIONS

[0001] Priority is claimed to provisional application Serial No.60/184,743, entitled “Injection Molding Techniques Utilizing FluidChannels,” No. 60/184,639, entitled “Integrated Co-Injection MoldedBumpers and Methods of Making the Same,” and No. 60/184,564, entitled“Low-Density Injection-Molded Body Parts,” which were all filed on Feb.24, 2000, and Serial No. 60/264,916, entitled “Multi-Part SequentialValve Gating,” which was filed Jan. 29, 2001.

FIELD OF THE INVENTION

[0002] The present invention relates to molding processes and anapparatus therefor. Specifically, the present invention relates toinjection molding processes and an apparatus which provide for increasedstrength of injection-molded articles that contain reinforcing fibers orparticles.

BACKGROUND OF THE INVENTION

[0003] Injection molding typically involves the injection of moltenresin through one or more gates to create multiple flow fronts withinthe mold. Flow fronts are the leading interface of a resin streamflowing within the mold. Multiple flow fronts may derive from multiplegates in the mold or from multiple flow paths communicating from asingle gate. As the molding process progresses, the flow frontseventually meet one another, resulting in the formation of one or moreknit lines.

[0004] In the prior art, knit lines represent areas of decreasedstrength in the molded article. In molding processes that utilize fiberreinforcement in the resin, fiber materials tend to align in thedirection of resin flow within the mold and typically do not becomeoriented or meshed across knit lines. As such, the use of injectionmolding to produce structural articles with fiber reinforced resins hasbeen somewhat problematic. For example, reinforcement structures invehicles are required to have rigid crossways linking the left and rightsides together and sufficient strength to support bumper fascias, grillecomponents, headlamps, radiator, washer fluid reservoir and othercomponents of the vehicle. Conventionally, such reinforcement structureshave been made from several stamped steel components welded together orfrom compression-molded continuous glass mat reinforced plastic.Although it has been recognized that injection molding techniquesgenerally result in a less-expensive and lighter-weight end product thanstamped-steel constructions or compression molding, conventionalinjection molding has not heretofore been widely employed for creatingstructural articles.

[0005] U.S. Pat. Nos. 5,556,650 and 5,417,916 teach an injection systemusing a single injection point for a fluid to displace a first portionof the molten plastic resin from a first portion of an article-definingcavity into a secondary portion of the article-defining cavity. Thereare limitations in using such a system having a single molten flow frontto make complex shaped articles. For example, injection of a pressurizedfluid may not adequately displace molten plastic resin through complexshaped articles. Further, knit lines can develop where flow fronts meet,resulting in decreased strength and structural integrity.

[0006] To summarize, articles that require increased strength andstructural integrity, such as structural polymeric articles likereinforcing members for automobiles, are difficult if not impossible tomake using conventional injection molding techniques.

[0007] Accordingly, it is a primary objective of the invention toprovide molding processes and apparatus for making injection moldedfiber-reinforced articles of increased strength as compared to articlesmade by prior art techniques.

SUMMARY OF THE INVENTION

[0008] The present invention provides processes and an apparatus forinjection-molding an article with a fluid channel formed therein toprovide strength and structural integrity. The process includesproviding a mold defining a mold cavity for a part or article, providingat least first and second resin streams within the mold cavity whereineach resin stream has a flow front, causing the flow fronts of the resinstreams to meet at a longitudinal point in the mold cavity to form afirst layer of solidified resin on a peripheral surface of the mold, thefirst layer having a knit line where the resin streams meet; andintroducing a fluid into the molten resin in the mold to form a fluidchannel and a second layer of solidified resin, the second layer betweenthe fluid channel and the first layer, wherein the second layer isdevoid of a knit line at the longitudinal point of the knit line in thefirst layer. Where desired, the fluid may be introduced and the resinmay be retained within the mold, or a portion of the resin can overflowoutside of the mold.

[0009] The fluid channel formed in accordance with the present inventionmay have a cross-section that is generally circular in shape and mayextend substantially through multiple portions of the molded article. Inaccordance with the present invention, orientation of reinforcing fibersin the second layer of solidified resin may be in a direction that isgenerally transverse to the knit line in the first solidified resinlayer. Further, the reinforcing fibers in the second layer of solidifiedresin can extend across the longitudinal point where the flow frontsmeet. The formation of the second layer of solidified resin that isdevoid of knit lines at the longitudinal point of the knit lines in thefirst layer of solidified resin results in increased enhanced structuralintegrity of the molded article. Further, the present invention can beused to make structural reinforcement articles, such as reinforcementmembers for vehicles, that could not be practically manufactured usingconventional injection molding techniques.

[0010] In a preferred embodiment, a molding apparatus according to theinvention includes a mold defining a mold cavity for a part or article,and at least one gate for introducing molten resin into the mold cavity.In a preferred embodiment, multiple gates can be used to introducemolten resin into the mold cavity. The mold is also provided with meansfor introducing a fluid, such as a compressed gas (for example, air ornitrogen) or a pressurized liquid (for example, water), into the moldcavity at an appropriate place and time. The fluid comprises a differentmaterial than the resin. Preferably, the fluid is introduced at a timewhen the resin that is immediately adjacent the mold cavity has begun tosolidify into a first layer of solidified resin due to the coolingprovided by the mold surface. The first layer of solidified resin isbetween the mold surface and resin near the center of the mold cavitythat is still in a molten state. As a result, injection of the fluidinto the mold cavity results in the displacement of the molten resinnear the center of the mold cavity and the formation of a fluid channel.

[0011] Displacement of the molten resin also results in a reorientationof reinforcing fibers in the molten resin in the vicinity of the knitlines in the first layer of solidified resin, such that when that moltenresin solidifies to form a second layer of solidified resin devoid of aknit line, fibers in the second layer are oriented transverse to theknit lines in the first layer. The displaced molten resin can be used tofill unfilled portions of the mold cavity to form first and secondlayers therein (a process that can be referred to as a “short shot” or“packing out” method) and/or the displaced resin can be displaced to anoverflow chamber (a process that can be referred to as an “overflow”method). Injection of fluid may occur through nozzles in fluidcommunication with the mold cavity and similar to those utilized forconventional gas-assisted molding techniques.

[0012] In one of its broadest applications, the invention provides anapparatus for injection molding articles comprising a mold including atleast a gate for the introduction of molten resin including reinforcingfibers, the resin traveling within the mold defining at least two flowfronts, the flow fronts meeting to form a knit line at a longitudinalpoint in a first layer of solidified resin, the first layer on theperipheral surface of the part being formed, and further including meansfor injecting a fluid into the resin within the mold to form a fluidchannel in the molded article, and a second layer of solidified resinbetween the fluid channel and the first layer of solidified resin, thesecond layer devoid of a knit line at the longitudinal point of the knitline in the first layer. Preferably, reinforcing fibers in the secondlayer may be orientated in a direction that is substantially transverseto the knit line.

[0013] In another of its broadest applications, the invention alsoprovides a process for injection molding articles, the processcomprising the steps of: a) providing a mold defining a mold cavity; b)providing first and second resin streams within the mold cavity, eachresin stream having a flow front; c) causing the flow fronts of theresin streams to meet to form a knit line at a longitudinal point in afirst layer of solidified resin; and d) introducing a fluid into theresin in the mold, and e) forming a fluid channel and a second layer ofsolidified resin, the second layer between the fluid channel and thefirst layer, the second layer devoid of a knit line at the longitudinalpoint of the first layer.

[0014] Co-injection of two or more different molten resins can also beused in accordance with the present invention to form different firstand/or second solidified resin layers at different portions of a part asmay be desired. More specifically, co-injection of two or more differentmolten resins can be performed at the same or different gate locationsand/or a different times as may be desired.

[0015] A primary advantage provided by the invention is increasedstrength of molded articles, especially at the longitudinal point ofknit lines, by forming a second layer devoid of a knit line at thatlongitudinal point of knit lines in the first layer. Thus, articlesmolded according to the invention will typically have greater strengthand structural integrity than articles molded according to conventionaltechniques. Moreover, articles that require increased strength andstructural integrity, such as structural polymeric articles forvehicles, may formed in accordance with the present invention that couldmot be made using conventional injection molding techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings which are incorporated into and form apart of the specification, illustrate preferred embodiments of thepresent invention and, together with the description, serve to explainthe principles of the invention. The drawings are only for the purposeof illustrating a preferred embodiment of the invention and are not tobe construed as limiting the invention. In the drawings, in which likenumbers refer to like parts throughout:

[0017]FIG. 1 is an illustration of a section taken along a moldcenterline and illustrating a process and apparatus for molding anarticle according to a preferred embodiment of the invention, showingthe introduction of molten resin into the mold;

[0018]FIG. 2A is an illustration of a section taken along a moldcenterline and illustrating a process and apparatus for molding anarticle according to a preferred embodiment of the invention, that is, apreferred “short shot” method, showing unfilled cavities prior to fluidinjection;

[0019]FIG. 2B is an illustration of a section taken along a moldcenterline and illustrating a process and apparatus for molding anarticle according to another preferred embodiment of the invention, thatis, a preferred “overflow” method, showing the formation of knit linesin a solidified outerlayer, and no knit lines in a liquid resin innerlayer prior to fluid injection;

[0020]FIG. 3 is an illustration of a section taken along a side view andillustrating a process and apparatus for molding an article according toa preferred embodiment of the invention, showing a fluid injectionapparatus for forming of a fluid channel;

[0021]FIG. 4 is a magnified view of a fluid channel 50 formed by theprocess and apparatus illustrated in FIGS. 1 through 3.

[0022] FIGS. 5-7 and 8-10 illustrate a process and apparatus for moldingan article using a “packing out” or “short shot” method and an“overflow” method, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023]FIG. 1 is a section taken along a mold centerline so as to revealthe back half of the mold 10 and the back half 11 of the mold cavity 14.The exemplary mold 10 is for a reinforcement member in a vehicle whichincludes a number of cross-members, associated with cross-member moldcavities 8 of mold cavity 14 which extend in a cross-vehicle direction,i.e., in a direction transverse to the plane of the driver and passengerdoors of the vehicle. The reinforcement member made in accordance withthe present invention can support a wide variety of components in avehicle, including but not limited to bumper fascias, battery, grillecomponents, headlamps, radiator, washer fluid reservoir and othercomponents of a vehicle. Generally, in the case of such reinforcementmembers, it is desirable to provide the greatest structural strength inthe cross-vehicle direction, which is generally indicated by the arrow(A). This is because the molded reinforcement member is typicallyutilized to support a number of components of the vehicle, including thebattery, windshield fluid reservoirs, headlights, etc. The reinforcingmember is also provided with a number of through holes associated withthrough hole projections 9 for mounting to the vehicle. It will berecognized by those of ordinary skill that the illustrated reinforcementis merely exemplary and it will be recognized that the invention findsbroad application to the molding of many other structural articles.

[0024] Mold 10 includes a number of gates 12 for introducing moltenresin 13 from a resin source 7 into the mold cavity 14. As can be seen,as molten resin is introduced into the mold through gates 12, a numberof flow fronts 16 are formed as the resin streams progress within themold cavity 14. While multiple gates 12 are shown, a single gate 12 canbe sued and still obtain multiple flow fronts 16 as the resin flowsthrough the cavity 14. Typically, the molten resin will comprisereinforcing fibers, such as glass and/or carbon fibers, or reinforcingparticles, such as nanoparticles (for example, nanoparticles comprisingsmectite clay), for increasing the structural strength of the moldedarticle. The resin can be any suitable resin, including but not limitedto polypropylene, polyethylene, and/or acrylonitrile butadiene styrene(ABS).

[0025]FIG. 2A is an illustration of a section taken along a moldcenterline and illustrating a process and apparatus for molding anarticle according to a preferred embodiment of the invention, that is, apreferred “short shot” method, showing unfilled cavities prior to fluidinjection. After fluid injection, knit lines (not shown) are formed asthe molten resin continues to flow within the mold cavity 14 and theflow fronts 16 collide. As will be recognized by those of ordinaryskill, the knit lines represent areas of weakened structural strength inarticles molded according to prior art techniques. Thus, the flow ratesof the molten resin into the gates 12 and the location of the gates 12are selected so that knit lines are formed in areas of the moldedarticle which are less likely to be subject to large forces. Further, asshown in FIG. 4, after fluid injection, the knit lines are formed in afirst layer 30 of solidified resin, but not in second layer 32 ofsolidified resin, thereby providing increased strength across knit lines20.

[0026]FIG. 2B is an illustration of a section taken along a moldcenterline and illustrating a process and apparatus for molding anarticle according to another preferred embodiment of the invention, thatis, a preferred “overflow” method, showing the formation of knit linesin a solidified outerlayer, and no knit lines in a liquid resin innerlayer prior to fluid injection. Further, as shown in FIG. 4, after fluidinjection, the knit lines are formed in a first layer 30 of solidifiedresin, but not in second layer 32 of solidified resin, thereby providingincreased strength across knit lines 20.

[0027]FIG. 3 is an illustration of a section taken along a side view andillustrating a process and apparatus for molding an article according toa preferred embodiment of the invention, showing a fluid injectionapparatus for forming of at least one fluid channel. The front half 18and the back half 11 of the mold 10 meet together to form the moldcavity 14. A fluid injection pin(s) 15 permits fluid injection at theappropriate time to form the desired fluid channel 50 as shown in FIG.4. A fluid injection control unit 40 is coupled to each fluid injectionpin 15 and provide control of the fluid from fluid source 41 so that thedesired fluid channels 50 are achieved.

[0028] Referring to FIG. 4, in accordance with an aspect of theinvention, the molded article is formed with one or more fluid channels50 extending substantially through the cross-member cavities 8 of themolded structure and across the knit lines 20. As will be appreciated bythose of ordinary skill in the art, the fluid channel 50 forms a verystrong fiber-reinforced tube within the molded article. Moreover, asillustrated in FIG. 4, the reinforcing fibers 22 extend across the knitlines 20, thereby strengthening the molded article at the knit lineinterface.

[0029] The formation of fluid channels 50 according to the invention,are accomplished by the use of one or more nozzles provided at or nearone end of cross member cavities 8, for injecting fluid into the moltenresin 13. Such nozzles are preferably of such a diameter or lateraldimension that their presence does not significantly impact thestructural strength of the molded article. Moreover, such nozzles may beprovided as retractable elements which may be retracted before theentire quantity of resin within the mold is cured, thereby providing forsome molten resin to migrate into the hole left by the nozzle.

[0030] It will be understood that the injection of fluid should occur ata time that is late enough in the molding process that the peripheralsurface of the molten resin has solidified or become semi-solid due tocooling by contact with the mold to form a first layer 30 before fluidinjection, yet early enough in the molding process that the center ofthe resin stream remains in a molten state. Introduction of fluidresults in displacement of the molten resin in a generally longitudinaldirection and across the knit line to form a second layer 32 ofsolidified molten resin after fluid injection.

[0031] As can be seen in FIG. 4, which is a magnified view of the fluidchannel 50 formed by the apparatus and method shown in FIGS. 1-3, theperipheral layer or first layer 30 of solidified resin has solidifiedwith knit line 20. The knit line 20 is a weakened area because the resinbegan to solidify at the surface of the flow fronts before meeting,resulting in weak fusion. The fibers 22 also do not cross the knit line20 in first layer 30. During the fluid injection stage, the fluiddisplaces resin that has not solidified, that is molten resin 13 incentral portion 52 (shown in FIGS. 7 and 10), through mold cavity 14. Asshown in the embodiment depicted in FIGS. 5-7, during the fluidinjection stage the displaced molten resin 13 continues to form a firstlayer 30 along the mold surface, and to form a second layer 32 insidethe peripheral layer or first layer 30 of solidified resin, wherein thesecond layer 32 is devoid of a knit line. As shown in the embodimentdepicted in FIGS. 8-10, during the fluid injection stage, displacedmolten resin overflows to an overflow chamber 19, while molten resinremaining the mold cavity forms second layer 32 inside the peripherallayers or first layer 30 of solidified resin, wherein the second layer32 is devoid of a knit line. The invention therefore provides forincreased strength in the vicinity of the knit lines 20 in the firstlayer 30 of solidified resin.

[0032] Injection of fluid to form a fluid channel in the mold may beaccomplished according to a “short shot” or “packing out” method asshown in FIGS. 2A and 5-7, or alternatively, according to an “overflowmethod” as shown in FIGS. 2B and 8-10. In the “packing out” methodillustrated in FIGS. 5-7, as the molten resin 13 flows from the materialmold gate 12, portions 34 of the resin begin to solidify to form firstlayer 30. As the molten resin 13 continues to flow into the mold cavity,more of the unfilled cavity 14 is filled. As the desired time, fluid isinjected via the fluid injection pin 15, forcing the molten resin 13toward the outside walls of the mold such that a fluid channel 50 isformed in the central portion 52 of the mold cavity 14 and a knit line20 is formed at a longitudinal point 25 in the mold cavity 14 where theflow front 16 meet. The remaining molten resin 13 then solidifies toform second layer 32 of solidified resin. As shown in FIG. 7, secondlayer 32 is devoid of a knit line. Part 100, which is formed accordingto this embodiment, thus has a second layer 32 of solidified resindevoid of a knit line in the vicinity of knit line 20 in first layer 30.Part 100 has increased strength and structural integrity due to thesecond layer 32 devoid of knit lines in the vicinity of knit line 20 infirst layer 30.

[0033] In the “overflow” method shown in FIGS. 2B and 8-10, while theoverflow valve 17 is closed, the molten resin 13 is inserted through thematerial mold gates 12. At a predetermined time when the molten resinhas filled a substantial portion of the mold cavity, the overflow valve17 is opened and fluid is injected via an injection pin(s) 15 to formthe desired fluid channel 50 substantially in the central portion of themolded component. The injected fluid displaces some molten resin 13 outof mold cavity 14 through overflow valve 17 and into overflow chamber19. Upon formation of the desired fluid channel 50, the resin adjacentto the walls of the mold has solidified in first layer 9300 and hasformed a knit line 20 at longitudinal point 25 in mold cavity 14 whereflow fronts 16 meet, and the overflow valve 17 is closed. The remainingmolten resin then solidifies to form second layer 32 of solidifiedresin. As shown in FIG. 10, second layer 32 is devoid of a knit line.Part 102, which is formed according to this embodiment, thus has asecond layer 32 of solidified resin devoid of a knit line in thevicinity of knit line 20 in first layer 30. Part 102 has increasedstrength and structural integrity due to the second layer 32 devoid ofknit lines in the vicinity of knit line 20 in first layer 30. Ifdesired, overflow chamber 19 can be grabbed by grabbers (not shown) toremove the part 102 from the mold. Overflow chamber 19 can be removedfrom part 102 using any suitable method, such as pulling off overflowholder 19 or trimming overflow chamber 19 from part 102.

[0034] As previously noted, the fluid can be either a compressed gas ora pressurized liquid. Liquids, such as water, cool and solidify themolten resin faster than a gas, thereby providing for shorter cycle timeto form a part. Further, a liquid, such as water, is heavier than a gas,and thus can more easily form a fluid channel in molten resin than agas. Thus, a liquid can form larger diameter and longer fluid channelsin a molten resin than a gas. After the second layer 32 has solidified,the fluid can be retained or expelled from the fluid channel as may bedesired.

[0035] Co-injection of multiple resin materials at the same or differentgates can be used in accordance with the present invention. Thus, ifdesired, the first layer 30 can comprise a different resin or resinmixture than the second layer 32. In addition, co-injection of multipleresin materials at the same or different times at the same or differentgates can be used in accordance with the present invention to obtainfirst layers 30 comprising a certain resin mixture at certain portionsof a part, as well as obtaining second layers 32 comprising a certainresin or resin mixtures at certain portions of a part as may be desired.In addition, the present invention can include sequential valve gatingas taught in U.S. Pat. No. 5,762,855, which is incorporated herein byreference.

[0036] The fluid(s) used to form the fluid channels in accordance withthe present invention can be allowed to exit the fluid channels afterthe first and second layers of solidified resins have been formed. Forexample, pressure exerted on a compressed gas used to form a fluidchannel can be released. A pressurized liquid can be simply be drainedfrom the fluid channel.

[0037] Although the preferred embodiments of this invention have beendescribed hereinabove in some detail, it should be appreciated that avariety of embodiments will be readily available to persons utilizingthe invention for a specific end use. The description of this inventionis not intended to be limiting on this invention, but is merelyillustrative of the preferred embodiment of this invention. Otherproducts, apparatus and methods which incorporate modifications orchanges to that which has been described herein are equally includedwithin this application. Additional objects, features and advantages ofthe present invention will become apparent by referring to the abovedescription of the invention in connection with the accompanyingdrawings.

What is claimed is:
 1. A process for injection-molding an article with afluid channel formed therein to provide strength and structuralintegrity, comprising the steps of: providing a mold defining a moldcavity; providing at least first and second molten resin streams withinthe mold cavity wherein each resin stream has a flow front; causing theflow fronts of the resin streams to meet at a longitudinal point in themold cavity and form a first layer of solidified resin on the peripheralsurface of the mold, the first layer having at least one knit line atthe longitudinal point where the resin fronts meet; and introducing afluid into either or both of the molten resin streams in the mold toform a fluid channel and a second layer, the second layer between thefirst layer and the fluid channel, the second layer devoid of a knitline at the longitudinal point where the resin fronts meet.
 2. Theprocess of claim 1 wherein the resin streams comprise reinforcingfibers.
 3. The process of claim 2 wherein the reinforcing fibers includeglass fibers.
 4. The process of claim 2 wherein the reinforcing fibersinclude carbon fibers.
 5. The process of claim 1 wherein the resinstreams comprise reinforcing particles.
 6. The process of claim 5wherein the reinforcing particles comprise nanoparticles.
 7. The processof claim 6 wherein the nanoparticles comprise smectite clay.
 8. Theprocess of claim 1 wherein the fluid is a compressed gas.
 9. The processof claim 1 wherein the fluid is a pressurized liquid.
 10. The process ofclaim 9 wherein the pressurized liquid is water.
 11. The process ofclaim 1 wherein the second layer has reinforcing fibers orientedtransverse to the knit line in the first layer and across thelongitudinal point in the mold cavity where the flow fronts meet.
 12. Anarticle formed using the process of claim
 1. 13. The article of claim 12wherein the article is a reinforcing member to support a vehiclecomponent in a vehicle.
 14. The process of claim 1 wherein introducingthe fluid is performed while the resin is maintained within the moldcavity.
 15. The process of claim 1 wherein introducing the fluid isperformed while some molten resin is allowed to exit the mold cavity asfluid is introduced into the mold.
 16. The process of claim 1 whereinthe first molten resin stream and the second molten resin stream areinjected into the mold cavity at the same location, the flow fronts ofthe resin streams meeting at a longitudinal point in the mold cavitydifferent than from the location of injection of the first and secondmolten resin streams.
 17. The process of claim 1 wherein the firstmolten resin stream is injected into the mold cavity a first location,and the second molten stream is injected into the mold cavity at asecond location, the first location being different than the secondlocation.
 18. The process of claim 1 wherein the first molten resinstream or the second molten resin stream, or both, comprise co-injectedresins.
 19. The process of claim 1 wherein the first molten resin streamand the second molten resin stream are injected into the mold cavity atdifferent gate locations around the mold cavity.
 20. The process ofclaim 1 wherein the first molten resin stream and the second moltenresin stream are injected into the mold cavity at different gatelocations around the mold cavity and using sequential valve gating. 21.An apparatus for injection-molding an article with a fluid channelformed therein to provide strength and structural integrity, comprising:a mold having a mold cavity with at least one mold gate for insertingmolten resin into the mold, the mold further comprising at least onefluid injection pin coupled to a fluid injection control unit having afluid source, wherein the molten resin is inserted into the at least onemold gate to provide at least first and second resin streams within themold cavity, each resin stream having a flow front such that when theflow fronts of the resin streams meet, a first layer of solidified resinis formed on a peripheral surface of the mold, and a knit line is formedin the first layer at a longitudinal point in the mold cavity where theflow fronts meet; and wherein a fluid is injected into the molten resinin the mold in a timely manner to form a fluid channel and a secondlayer of solidified resin, the second layer between the fluid channeland the first layer, wherein the second layer is devoid of a knit lineat the longitudinal point where the flow fronts meet.
 22. The apparatusof claim 21 further having at least one resin stream source for resinstreams comprising reinforcing fibers.
 23. The apparatus of claim 22wherein the reinforcing fibers include glass fibers.
 24. The apparatusof claim 22 wherein the reinforcing fibers include carbon fibers. 25.The apparatus of claim 21 further having at least one resin streamsource for resin streams comprising reinforcing particles.
 26. Theapparatus of claim 25 wherein the reinforcing particles comprisenanoparticles.
 27. The apparatus of claims 26 wherein the nanoparticlescomprise smectite clay.
 28. An article formed using the apparatus ofclaim
 21. 29. The article of claim 28 wherein the second layer hasreinforcing fibers oriented transverse to the knit line in the firstlayer and across the longitudinal point in the mold cavity where theflow fronts meet.
 30. The article of claim 28 wherein the article is areinforcing member to support a vehicle component in a vehicle.
 31. Theapparatus of claim 21 wherein the fluid source comprises a compressedgas.
 32. The apparatus of claim 21 wherein the fluid comprises apressurized liquid.
 33. The apparatus of claim 32 wherein thepressurized liquid is water.
 34. The apparatus of claim 21 wherein themold further includes an overflow valve to allow some molten resin toexit the mold cavity as fluid is introduced into the mold.